1. Field of the Invention
The present invention relates to a hybrid drive unit for transmitting torques from a plurality of power sources including an internal combustion engine and an electric motor to an output member such as an output shaft and, more particularly, to a control system for controlling the applications/releases of engagement elements of a hybrid drive unit which is constructed such that torque transmission lines from the power sources to the output shaft are changed by the applications/releases of the engagement elements such as clutches or brakes to be applied by a hydraulic pressure.
2. Related Art
A hybrid vehicle using an internal combustion engine such as a gasoline engine and an electric motor as power sources and having an electric generator mounted thereon has been developed and practiced as a vehicle which is enabled to reduce the exhaust gas (i.e. emission) and improve the fuel consumption by running the internal combustion engine efficiently and by regenerating the energy. The hybrid vehicle of this kind is basically constructed to effect the efficient run by changing the power sources to be used on the basis of the running state. In order to reduce the size and improve the power performance, however, it has been widely tried to use a transmission together.
As this transmission, there have been a variety of constructions including not only an ordinary transmission for changing the gear ratio discontinuously or continuously but also a construction in which the torque of the internal combustion engine and the torque of the electric motor are synthesized and outputted, a construction in which the torque of the internal combustion engine is amplified and outputted, and a construction in which a reverse step is set. By using these transmissions together, the torque transmission lines can be made more various to set drive states for satisfying the various demands. In this case, too, it is necessary to reduce the size and weight of the entire system. Therefore, the construction may be modified such that the engagement elements for holding the torque transmission lines are applied both for the forward run and for the backward run, or such that the valves for feeding application pressure such as oil pressures to predetermined engagement elements are applied both for the forward run and for the regeneration of the energy. In short, the engagement elements and the valves for controlling the elements are used in different drive states. As a result, the drive state of the vehicle may be inverted, when the control valves are inverted from the intrinsic action state by some disorder or when the applied states of the engagement elements become different from the intrinsic states.
In order to prevent this inversion of the drive states, as might accompany the so-called xe2x80x9cfailurexe2x80x9d, the invention, as described in Japanese Patent Laid-Open No. 10-103507, is constructed such that the oil pressure is drained when a valve sticks during the forward run or during the backward run. Specifically, the front shift valve is constructed to be switched between the position where the oil pressure is fed to the front clutch and drained from the rear clutch and the position where the front clutch is blocked from the line pressure, and the rear shift valve is constructed to be switched between the position where the oil pressure is fed to the rear clutch and drained from the front clutch and the position where the rear clutch is blocked from the line pressure. When each shift valve sticks into the state in which the oil pressure is fed to each of the front and rear clutches, therefore, the oil pressure is drained individually from the front and rear clutches so that a neutral state is established to avoid the trouble due to the valve stick.
The invention, as described in the aforementioned Laid-Open, provides the construction for establishing the fail-safe in the case where the control for the backward run by inverting the torque outputted from the engine and transmitting it to the output side and the control for the forward run by transmitting the torque outputted from the engine to the output side without inverting are simultaneously caused by the valve stick. In the hybrid vehicles, however, the situations for the fail-safe to be established are more various because the powers are inputted from the plurality of power source to the gear mechanism of the transmission, or because in the hybrid vehicle using an internal combustion engine and a motor/generator as the power sources, the power generation and the power charge may be performed by driving the motor/generator by the internal combustion engine. Specifically, this so-called xe2x80x9ccharging modexe2x80x9d is executed not depending on whether the vehicle is running or not but on the charging state of the battery, and the vehicle may run, even during the stop, if the failure is caused by the valve stick or the like. This is a situation peculiar to the hybrid vehicle and cannot be solved by the construction for the fail-safe which is directed to the vehicular transmission using only the engine as the power source, as described in the Laid-Open.
A main object of the invention is to provide a control system for a hybrid control unit for avoiding it in advance that drive state is made different from the intended one by a trouble in a control system of a hydraulic pressure to apply engagement elements.
Another object of the invention is to provide a control system for a hybrid drive unit, which is constructed such that the feed passages of a hydraulic pressure to a plurality of engagement elements for establishing a predetermined drive state are selected by a manually operable switching valve.
According to the invention, there is provided a control system for a hybrid drive unit, comprising: a gear mechanism having different rotary members connected to a plurality of power sources; and a plurality of engagement elements adapted to be applied by a hydraulic pressure for coupling the rotary members to each other in the gear mechanism and for stopping rotations of a predetermined rotary member, wherein in accordance with the applied/released states of the engagement elements, there can be set: a forward running range for a forward run by inputting an input torque to an output member; a backward running range for a backward run by transmitting an input torque to the output member; and a stop range capable of driving one of the power sources by the other. The control system further comprises a range switching valve activated in response to the individual set ranges for switching and outputting an initial pressure for applying the engagement elements, to a plurality of passages, and adapted, when the stop range is set, to output a hydraulic pressure to the engagement element for establishing a torque transmission passage from one of the power sources to the other and to block the feed of the initial pressure to the engagement element for establishing, when applied, the torque at the output member.
Therefore, the individual engagement elements are fed with the initial pressure for applications in accordance with the range, as set, from the range switching valve. With the stop range being set, moreover, when one power source is to be driven by another in the stop range, the engagement elements are so applied as to transmit the torque between those power sources. At this time, even if any trouble occurs in the feed line of the hydraulic pressure to the engagement element which will generate, if applied, the torque at the output member to invite the situation in which the hydraulic pressure is applied to the engagement element, the output of the initial pressure for the application to the troubled engagement element is blocked by the range switching valve for outputting the initial pressure, so that the engagement element is kept in the released state. In short, it is possible to avoid it in advance that the torque is generated at the output member with the stop range being set.
According to the invention, on the other hand, there can be provided a control system for a hybrid drive unit, wherein the torques outputted by an internal combustion engine and an electric motor are selectively transmitted in accordance with a selected one of a forward running range, a stop range and a backward running range through a planetary gear mechanism to an output member. The control system can further comprise: a first engagement element adapted to be applied by a hydraulic pressure for establishing a forward running state by coupling the rotary elements of the planetary gear mechanism or the rotary elements and another member; a second engagement element adapted to be applied by a hydraulic pressure with the first engagement element being applied, for establishing a reverse running state by coupling the rotary elements of the planetary gear mechanism or the rotary elements and another member; and a range switching valve adapted to be activated in response to each of the ranges and including a plurality of output ports for outputting the initial pressure of the hydraulic pressure in accordance with the range selected, and for opening the output port leading to the first engagement element and dosing the output port leading to the second engagement element, when the forward running range is selected.
In the control system, therefore, the forward running state is established when the first engagement element is applied, and the reverse state is established when both the first engagement element and the second engagement element are applied, so that the drive state is reversed depending upon whether or not the second engagement element is applied. With the forward running range is selected, on the contrary, the range switching valve closes the output port leading to the second engagement element but opens the output port leading to the first engagement element. In the forward running range, therefore, the feed of the hydraulic pressure to the second engagement element is prevented by the range switching valve for controlling the feed of the initial pressure. As a result, it is possible to prevent it in advance that the reverse state is established despite that the forward running range is selected.
According to the invention, moreover, there can be provided a control system for a hybrid drive unit, wherein an internal combustion engine is connected to any of three rotary elements constructing a planetary gear mechanism whereas an electric generator is connected to another of the rotary elements, so that the torque is selectively outputted in accordance with a selected one of a forward running range, a stop range and a backward running range, through the planetary gear mechanism to an output member. The control system can comprise: a first engagement element adapted to be applied by a hydraulic pressure for selectively connecting the output member and any of the rotary elements of the planetary gear mechanism; a second engagement element adapted to be applied by a hydraulic pressure for bringing the torque of the internal combustion engine into a state where the torque can be transmitted to the electric generator; and a range switching valve adapted to be activated in response to each of the ranges and including a plurality of output ports for outputting the initial pressure of the hydraulic pressure in accordance with the range selected, and for closing the output port leading to the first engagement element and opening the output port leading to the second engagement element, when the stop range is selected.
In this control system, therefore, with the drive range being selected, the first engagement element is applied so that the torque can be transmitted to the output member to effect the forward run or the backward run. With the stop range being selected, on the other hand, the output port leading to the first engagement element in the range switching valve is closed to open the first engagement element, but the output port leading to the second engagement element is opened to apply the second engagement element. As a result, the torque of the internal combustion engine can be transmitted to the electric generator to generate the electric power. In short, the vehicle can be reliably prevented from running even if the internal combustion engine is activated, while generating the electric power.
According to the invention, moreover, there can be provided a control system for a hybrid drive unit, wherein the torques outputted by an internal combustion engine and an electric motor are selectively transmitted in accordance with a selected one of a forward running range, a stop range and a backward running range through a planetary gear mechanism to an output member. The control system can comprise: a first engagement element adapted to be applied by a hydraulic pressure for establishing a forward running state by coupling the rotary elements of the planetary gear mechanism or the rotary elements and another member; a second engagement element adapted to be applied by a hydraulic pressure with the first engagement element being applied, for establishing a reverse running state by coupling the rotary elements of the planetary gear mechanism or the rotary elements and another member; and a range switching valve adapted to be activated in response to each of the ranges for outputting an initial pressure of the hydraulic pressure and for closing a predetermined output port leading to the first engagement element, opening a port for outputting the hydraulic pressure to the second engagement element, and opening another port for feeding a portion of the hydraulic pressure, as outputted from the port, to the first engagement element.
In this control system, therefore, the forward running state is established by applying the first engagement element, and the backward running state is established by applying the first engagement element and the second engagement element. When the reverse range is selected, moreover, the first engagement element is fed via another port of the range switching valve with a portion of the hydraulic pressure to be fed from the range switching valve to the second engagement element. In the reverse range, specifically, the hydraulic pressure is not fed to the first engagement element before there is established the feed state of the hydraulic pressure for applying the second engagement element. The reverse range does not come into the feed state of the hydraulic pressure for establishing the forward running state.
The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read with reference to the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention.